1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method of producing the electrophotographic photosensitive member, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
In recent years, for the purpose of extending the life of an electrophotographic photosensitive member, improving image quality, and increasing the processing speed of an electrophotographic apparatus, it has been desired to improve the durability of an organic electrophotographic photosensitive member containing an organic photoconductive substance (charge generating substance) (hereinafter referred to as an “electrophotographic photosensitive member”).
The improvement of the durability of the electrophotographic photosensitive member may be an improvement of mechanical durability, such as resistance to abrasion and scratches, an improvement of electric potential stability during repeated charging and discharging of electricity, or the prevention of image deletion caused by discharge products resulting from charging, such as ozone and nitrogen oxide. There is a demand for an electrophotographic photosensitive member that satisfies both the improvements of mechanical durability and electric potential stability and the prevention of image deletion in order to achieve an electrophotographic photosensitive member having excellent image stability.
Japanese Patent Laid-Open No. 2000-066425 discloses a technique for providing a surface layer with a polymer produced by the polymerization of a charge transporting substance having two or more chain-polymerizable functional groups (acryloyloxy groups and/or methacryloyloxy groups) to improve the mechanical durability (abrasion resistance) and the electric potential stability of an electrophotographic photosensitive member. Japanese Patent Laid-Open No. 2010-156835 discloses a technique for providing a surface layer with a charge transporting substance having two or more methacryloyl groups per molecule and a polymer of a composition containing no polymerization initiator to improve the mechanical durability (abrasion resistance) and the electric potential stability of an electrophotographic photosensitive member.
The present inventors found that, among the chain-polymerizable charge transporting substances described in Japanese Patent Laid-Open No. 2000-066425, a charge transporting substance having a methacryloyloxy group can more improve mechanical durability and allows an electrophotographic photosensitive member to be used more times than a charge transporting substance having an acryloyloxy group. However, the present inventors also found that a charge transporting substance having a methacryloyloxy group has more room for improvement in terms of image deletion, memory, and spot leakage (leakage that causes spots in output images) resulting from an increase in the number of times an electrophotographic photosensitive member is used. A charge transporting substance having two or more methacryloyl groups used in Japanese Patent Laid-Open No. 2010-156835 tends to cause distortion of the layer and consequently memory and spot leakage. It was also found that the prevention of image deletion must be improved.